RESUMEN
Geopolymer concrete is a sustainable construction material developed with industrial by-products to eliminate the use of cement in concrete production. However, a cradle-to-cradle life cycle assessment (LCA) that accounts for the impact of service life is essential to comprehensively assess the environmental advantages of GPC. In this study, a comparative cradle-to-cradle LCA was performed for circular geopolymer concrete (CGPC), geopolymer concrete (GPC), and circular ordinary concrete (COC), as alternatives to Portland cement concrete (PCC). Also, the biases of common LCA resulted from ignoring service life and end-of-life scenarios were identified. Finally, the sustainability potentials of the alternative scenarios were evaluated. According to the cradle-to-cradle LCA using the adopted functional unit, GPC and CGPC significantly alleviated the environmental impact of cement production, such as global warming potential by about 53%. Ignoring the service life and end-of-life scenarios considerably changed the critical midpoint (ionizing radiation for CGPC and GPC) and endpoint indicators (resources for CGPC and GPC) and priority of alternative concretes. Finally, the CGPC and GPC showed a substantial increase of 213% and 276% in sustainability potential compared to PCC, respectively.
RESUMEN
Concrete is the most consumed material in the construction industry. Using recycled aggregates (RA) and silica fume (SF) in concrete and mortar could preserve natural aggregates (NA) and reduce CO2 emissions and construction and demolition waste (C&DW) generation. Optimizing the mixture design based on both fresh and hardened properties of recycled self-consolidating mortar (RSCM) has not been performed. In this study, multi-objective optimization of mechanical properties and workability of RSCM containing SF was performed via Taguchi Design Method (TDM) with four main variables including cement content, W/C ratio, SF content and superplasticizer content at three different levels. SF was used to decrease the environmental pollution caused by cement production as well as compensating the negative effect of RA on the mechanical properties of RSCM. The results revealed that TDM could appropriately predict the workability and compressive strength of RSCM. Also, mixture design containing W/C = 0.39, SF = 6%, cement = 750 kg/m3 and SP = 0.33% was found as the optimum mixture having the highest compressive strength and acceptable workability as well as low cost and environmental concerns.
RESUMEN
In this research, the effectiveness of using pervious concrete as a reactive barrier to decrease the concentration of nitrates in polluted water was investigated. Parameters of concrete mix design including water to cement ratio (W/C), aggregate to cement ratio (A/C), the amount of nano-silica (NS), and fine aggregates (FA) were studied based on Taguchi method. Properties of concrete such as compressive strength, density, permeability, and porosity, as well as pH measurement and the column method were carried out to assess the nitrate removal capacity of pervious concrete. Also, SEM-EDX, XRD, and FTIR were used to analyze the results. It was found that the optimum mix design in terms of nitrate removal corresponded to the mix with W/C = 0.26, A/C = 5, NS = 6%, and FA = 20%. Based on the results, it can be said that adding NS (up to 6%) and FA (up to 20%) to pervious concrete had the best influence on nitrate removal and compressive strength. Addition of NS increased the nitrate removal capacity due to increase in surface positive charges and provision of new surface functional groups.